Search for gas in Triassic reefs progresses in northern Israel

Feb. 18, 2002
A private independent is exploring what it calls a significant Triassic reef trend in northern Israel.

A private independent is exploring what it calls a significant Triassic reef trend in northern Israel.

Making the play is Zion Oil & Gas Inc., Dallas, which states that preliminary results of geologic work and seismic interpretation indicate the trend could contain several trillion cubic feet of gas and several hundred million barrels of liquids.

An onshore discovery of this caliber would be another big event for Israel, which had only minor commercial production of oil and gas to show after the drilling of more than 400 onshore wells in 50 years. Several large offshore gas discoveries in 1999-2000 changed perceptions of the country's potential.

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The Triassic onshore play does not relate geologically to the offshore play, which involves Tertiary Pliocene and Miocene rocks similar to those that contain major reserves in the Nile Delta province along Egypt's north coast.

Zion's studies indicate that hydrocarbon volumes recoverable from the reef trend could be as large as those in the offshore fields, notwithstanding the differences in geologic age and depth.

Zion hopes to drill its first well or re-enter an existing well in 2002. Israel's electric power generation industry appears to provide an adequate market for gas.

The company lists principals in the US and Israel. They include President Eugene A. Soltero, formerly of Cimarron Resources Inc., Cotton Valley Resources Corp., and Aztec Energy Corp.; Executive Vice-Pres. Glen H. Perry, formerly with Exxon Co. USA and Energy Reserves Group Inc.; and Jack Sherman, senior geological consultant (OGJ, Jan. 7, 2002, p. 34).

Onshore acreage

Israel awarded Zion a preliminary permit with priority rights on May 1, 2001, that covers 137,250 acres north of Tel Aviv known as the Joseph Permit (Fig. 1).

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The permit bounds the 28,800-acre Ma'anit License, awarded to Zion a year earlier, on three sides. Ma'anit has an initial term of 3 years. It is convertible to a 30-year lease upon completion of a commercial discovery and extendable a further 20 years.

Together referred to as the Joseph Project, the two areas lie inside Israel's pre-1967 border between the coast and the Jezreel Valley.

On the Ma'anit License are Ma'anit-1 and Har Amir 1, two abandoned exploratory wells drilled to Middle Jurassic.

Zion from May 2000 through April 2001 correlated and mapped 250 km of seismic lines, reprocessed 70 km of existing seismic lines, and acquired 11 km of new seismic lines.

Play concept

The main target on Ma'anit is a buried platform or barrier reef more than 8,000 ft thick. The reef has five distinct highs and is thought to be sealed by shales and anhydrites of Upper Triassic and Lower Jurassic.

Other targets include the Lower Jurassic Nirim formation and the Lower Triassic Ra'af formation.

The main carbonate reef objective represents a significant departure from the conventional understanding of the area as originally postulated by a study released in 1988 by Oil Exploration Investment Ltd., Zion said. OEIL, a government entity, was formed to conduct a comprehensive basin analysis of Israel and then disbanded.

Stoakes Consulting Group Ltd., Calgary, studied Zion's play concept, seismic lines, interpretations, and work product in July-October 2001. Stoakes' report corroborates Zion's interpretive work and "concludes that the Ma'anit reef, as interpreted from the best seismic line, may be larger and thicker than previously estimated," Zion noted.

Upside potential for a gas-condensate reservoir discovery in the Ma'anit reef and the Ra'af formation on the Ma'anit License alone is 2-2.5 tcf of gas plus 100 million bbl or more of condensate or oil. Based on preliminary information available in the Joseph Permit, there appears to be a potential for similar or greater quantities of hydrocarbons in four leads seen there, Zion said.

Exploration history

Israel hosted its first drilling in 1947 and completion of its first discovery in 1955 at Heletz.

Of 410 wells drilled to 1,500-21,000+ ft, the vast majority have been shallow wells drilled on surface geology.

The results:

  • Numerous noncommercial shows in many wells.
  • Small commercial production of oil at Heletz, Kokhav, Ashdod, and Zuk Tamrur.
  • Small commercial production of gas at Zohar, Kidod, Kanaim, Sadot, Ashdod, Shiqma, Notera, and Hula Valley (Mazal).
  • World-class offshore gas discoveries at Noa, Or, Ashqelon (Mari-B), and Nir (Table 1).

Exploration in the 1940s-60s began for objectives in Cretaceous formations mainly in the Negev desert and later in Upper and Middle Jurassic formations, resulting in discovery of the first gas fields and a further oil find at Kokhav.

Exploration in the 1970s-80s in the Sinai and Gulf of Suez resulted in discovery of Alma oil field and Sadot gas field, and on the Israeli coastal plain, Shiqma gas field and Ashdod oil field.

Exploration near the Dead Sea resulted in live oil recoveries from Triassic tests but no commercial discovery.

Atlit-1, a deep well drilled in northern Israel in the early 1980s, flowed asphalt from the top of Triassic and had 300 ft of strong oil shows in Upper Triassic before being abandoned due to hole problems. Ramallah-1 and Deborah-1 had oil shows in either Jurassic or Triassic formations.

Zuk Tamrur field, found in the 1990s near the Dead Sea, ultimately produced 250,000 bbl of light oil from Ra'af.

In the area from Tel Aviv northward, several 1990s wells had shows in Triassic. Sedot Neft attempted to drill a Triassic test at Ma'anit but ran out of funds at TD 7,660 ft before reaching the objective. Zion owns rights to the Ma'anit well in connection with its license and might deepen it to Triassic targets at 13,000 and 16,400 ft.

Zion's long range plans include more seismic surveys and two to four more wells.

Barrier reef system object of exploration

Zion Oil & Gas Inc., Dallas, as of late January 2002 had completed the inputting of 450 km of seismic lines into Paradigm and Landmark workstations at the Israeli Geophysical Institute.

Based on reprocessing and model work so far, Zion has developed a radically different approach to exploration in Israel. Whereas in the past analogy has been Africa and the Middle East, Zion has turned to the west and the Proto-Tethys sea of the Triassic.

In doing so, Zion has identified, on seismic, a carbonate platform sill between the shallow open sea to the west and a subsiding evaporitic basin to the east. The platform provided the base for reefal development, and the result was a barrier reef system that remained intact over geologic time.

From the work done so far, this barrier reef is believed to encompass an area of at least 40 by 12 km. Reefal thicknesses appear to vary between 50 and 650 m. Porosity is indicated within the reef margins.

The system is structurally high to the Levant basin to the west and the Triassic/Paleozoic basin to the east, and the reefs are overlain by impermeable formations.

Source rocks may include some Triassic shales and the deeper Silurian shales of the Paleozoic. The exploration targets include the porous and permeable reef margins and the back reef talus in the subsiding basin.

Within the 166,000 acres of petroleum rights Zion holds, more than 6 million acre-ft of reefal margins are potentially productive and in hydrodynamic communication. If oil, this could mean an upside potential of 400 million bbl and 2 tcf of associated gas, or if gas 4 tcf and 200 million bbl of associated liquids. Geochemical analysis from nearby wells favors the presence of oil at 13,000-14,000 ft.

Two specific reef prospects have been identified and delineated. The first contains 6,000 acres located above a known Paleozoic high which a prior operator attempted to drill and ran out of money after lining the hole with 13-5/8 in. casing to 7,500 ft. The second has 12,000 acres of seismic closure.

Drilling of the first prospect is scheduled for the second half of 2002.

Zion is showing the prospect to industry players. It seeks to place 10-25% with US independents and up to 20% with an Israeli downstream company. Zion will retain the remainder and is raising equity funds to pay its share of the drilling, a portion of which funds have already been raised.